Streptococcus spp.

Overview

Streptococcus spp. is a genus of gram-positive, facultatively anaerobic bacteria commonly found in pairs or chains. The primary distinctions between beneficial and pathogenic Streptococcus species lie in their physiological effects, ecological niches, and interactions with the human host. Beneficial species generally contribute to human health either through direct probiotic actions or by aiding in food digestion and preparation. In contrast, pathogenic species are associated with a range of diseases and often require medical intervention to manage infections effectively. Important human pathogens include Streptococcus pneumoniae, Streptococcus pyogenes (group A strep), and Streptococcus agalactiae (group B strep). Streptococcus species are diverse in their pathogenic potential and categorized based on their hemolytic properties and bacterial antigens found on their cell walls.^[x]

What species of Streptococcus are known to be beneficial?

Beneficial Streptococcus Species	Description
Streptococcus salivarius	Often found in the mouth and upper respiratory tract, this species is considered beneficial for its role in colonizing the oral cavity soon after birth, which can help outcompete more harmful bacteria. It is used as a probiotic in some products to improve oral health and prevent sore throat.
Streptococcus thermophilus	This is a major culture used in the production of yogurt and cheese. It is non-pathogenic and beneficial for gastrointestinal health, and plays a role in the gut-eye axis.^[x]Streptococcus thermophilus also aids in the digestion of lactose and is associated with producing anti-inflammatory effects in the gut.

Virulence Factors

Streptococcus species exhibit several virulence factors critical to their pathogenicity. M Proteins, particularly in Streptococcus pyogenes, are surface proteins that obstruct phagocytosis, playing a crucial role in the bacterium’s virulence. Additionally, polysaccharide capsules, which are notably prominent in Streptococcus pneumoniae, also inhibit phagocytosis. In S. pyogenes, the hyaluronic acid capsule mimics human connective tissue, thus facilitating the evasion of the immune response. S. pneumoniae produces pneumolysin, a toxin that induces cell lysis and contributes significantly to inflammation and tissue damage. Further, streptolysins, a group of hemolysins produced by Streptococcus, can lyse red and white blood cells, causing further tissue destruction. These factors underscore the sophisticated mechanisms by which Streptococcus species evade immune defenses and establish infection.

Pathogenic Streptococcus Species	Virulence Factors and Associated Conditions
Streptococcus pyogenes (Group A)	Produces toxins and enzymes such as streptolysin, which causes cell lysis. Associated with conditions such as strep throat, scarlet fever, rheumatic fever, and necrotizing fasciitis.
Streptococcus pneumoniae	Capsule prevents phagocytosis, pneumolysin damages respiratory epithelial cells. Leads to pneumonia, meningitis, otitis media, and sinusitis.
Streptococcus agalactiae (Group B)	Capsular polysaccharide inhibits phagocytosis. Known for causing neonatal sepsis, pneumonia, and meningitis in newborns.

Ion Acquisition Systems

Iron availability within the human host is limited due to tight regulation and sequestration by host proteins such as transferrin, lactoferrin, and ferritin, which reduce free iron to inhibit bacterial growth. However, like many other pathogens, these bacteria require various metal ions, particularly iron, for essential biological processes. Iron is especially critical because it comprises proteins and enzymes involved in DNA synthesis, respiration, and other metabolic pathways. By securing necessary resources like iron from the host, Streptococcus species can proliferate and establish infections, contributing to their virulence. As such, metal ion acquisition systems play a crucial role in metal homeostasis, and the survival and pathogenicity of Streptococcus species. Thus, targeting these systems can be a viable strategy in developing novel therapeutic approaches to combat streptococcal infections.

What iron acquisition systems are used by Streptococcus spp?

Iron Acquisition System	Description
ABC Transporters	These systems transport complexed iron across the bacterial membrane.
Hemolysins	Break down host hemoglobin to release iron.
Neuraminidases	Enzymes that enhance liberation and uptake of iron from host cells by altering cell surface properties.

Associated Conditions

Streptococcus species are associated with a wide range of health conditions, affecting various body systems. These bacteria can cause both mild and severe infections, ranging from common throat infections, to endometriosis, to life-threatening diseases. The conditions they cause vary based on the Streptococcus species involved. The wide pathogenic potential of these bacteria highlights their significance in clinical microbiology and public health.

What are some conditions commonly attributed to Streptococcus spp. infection?

Streptococcus Species	Associated Conditions
S. pyogenes (Group A)	Strep throat, Scarlet fever, Rheumatic fever, Impetigo, Necrotizing fasciitis
S. agalactiae (Group B)	Neonatal sepsis, Meningitis in newborns, Pneumonia in newborns
S. pneumoniae	Pneumonia, Sinusitis, Otitis media, Meningitis
S. mutans	Dental caries
S. viridans	Subacute bacterial endocarditis

Interventions

The continuous emergence of antibiotic resistance in Streptococcus spp. underscores the importance of developing new therapeutic strategies. Research into the molecular mechanisms of resistance and pathogenicity, alongside novel treatment modalities, remains crucial in the ongoing effort to manage infections caused by these bacteria effectively.

What interventions are effective against Streptococcus spp?

Intervention Type	Mechanism or Description
Beta-lactams (penicillins, cephalosporins)	Inhibit cell wall synthesis, preventing bacterial growth.
Macrolides (erythromycin)	Inhibit protein synthesis by binding to the bacterial ribosome.
Fluoroquinolones	Inhibit DNA gyrase, affecting DNA replication.
Terpenes (e.g., thymol, menthol)	Disrupt bacterial membranes and inhibit enzyme activity, found in essential oils.
Photobiomodulation	Induce photochemical reactions that reduce bacterial growth, enhance tissue repair, and modulate inflammation. Blue light can produce reactive oxygen species to kill bacteria, including drug-resistant strains.

What terpenes have been clinically investigated for Streptococcus spp. infections?

Terpenes are a diverse class of naturally occurring organic compounds, mainly found in essential oils derived from plants. They have been extensively investigated for their antimicrobial properties, including their activity against various bacterial species such as Streptococcus spp. The clinical investigations into terpenes have shown promising results in controlling bacterial growth, particularly in oral and dental applications. These compounds are appealing due to their natural origin, which often makes them more acceptable to consumers looking for “natural” treatments. Terpenes offer a supplementary approach to traditional antibiotics in the context of Streptococcus spp., potentially reducing the risk of resistance development. However, future research should focus on their synergistic effects with conventional antimicrobials, optimal dosing strategies, and effectiveness in systemic infections beyond the oral cavity.

Thymol: Derived from Thyme (Thymus vulgaris), thymol has demonstrated strong antibacterial activity, particularly against Streptococcus mutans, a key bacterium involved in dental caries. Its mechanism includes disrupting the bacterial cell membrane and inhibiting enzyme activity.^[x]

Carvacrol: Carvacrol, found in oregano oil (Origanum vulgare), is similar to thymol, disrupting the cell membrane and inhibiting the growth of Streptococcus spp. It has been noted for its efficacy against Streptococcal infection. ^[x]

Farnesol: Farnesol is a constituent of essential oil derived from various plants such as citronella, lemon grass, tuberose, cyclamen, rose, neroli, balsam, and musk with anti-inflammatory and anti-cancer activity. [x] Farnesol has shown significant antimicrobial activity against several bacteria, including those notorious for antibiotic resistance, with the ability to inhibit the biofilm formation of Streptococcus spp.^[x] Notably, these derivatives enhanced the effectiveness of β-lactam antibiotics such as oxacillin. Combined with these antibiotics, farnesol derivatives significantly reduced the oxacillin MIC by up to 128-fold against resistant strains, highlighting their potential utility as adjuncts in antibiotic therapy. ^[x]

Menthol: Extracted from peppermint oil (Mentha piperita). Acts by altering the cell membrane structure of bacteria, thereby disrupting cellular processes. Menthol is used in throat lozenges and various oral hygiene products for its soothing properties and its ability to inhibit oral pathogens, including Streptococcus species. [x]

Eugenol: Found in clove oil (Syzygium aromaticum), eugenol has been noted for its ability to disrupt the cell walls and membranes of Streptococcus spp., leading to the leakage of essential intracellular components. Eugenol is often used in dentistry for its analgesic, anti-inflammatory, and antimicrobial properties, particularly in root canal sealers and periodontal therapies. ^[x]

1-8 Cineole (Eucalyptol): Found in eucalyptus oil, cineole interferes with cell membrane function and enzymatic activity, leading to bacterial death. Used in cough syrups and dental hygiene products for its antimicrobial and anti-inflammatory properties. ^[x]

FAQs

What else should I know about Streptococcus spp.? Streptococcus spp. infections can be associated with anemia, although it is not the most commonly highlighted complication.

What mechanisms explain anemia due to a Streptococcus spp. infection?

Chronic Disease: Chronic infections can lead to anemia of chronic disease (also known as anemia of inflammation). This type of anemia is mediated by the immune response to infection, where inflammatory cytokines interfere with iron metabolism and erythropoiesis.

Hemolytic Anemia: Certain strains of Streptococcus, notably some belonging to Streptococcus pneumoniae, produce toxins that can lead to the destruction of red blood cells, resulting in hemolytic anemia. This occurs when the bacterial toxins damage erythrocyte cell membranes, leading to premature destruction.

Nutritional Deficiency: Infections can affect the body’s nutritional status by reducing appetite or increasing nutrient requirements, contributing to deficiency-related anemia, particularly iron deficiency anemia.

Research Feed

June 13, 2020

Microbes •

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